BTThreeDSecureDriver: Set completion block to nil after executing when an error occurs.
BTThreeDSecureDriver: Set completion block to nil after executing when an error occurs.

braintree/braintree_ios,apascual/braintree_ios,braintree/braintree_ios,billCTG/braintree_ios,braintree/braintree_ios,billCTG/braintree_ios,billCTG/braintree_ios,billCTG/braintree_ios,apascual/braintree_ios,braintree/braintree_ios,billCTG/braintree_ios,apascual/braintree_ios,apascual/braintree_ios